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Classes and interfaces for the Core JSP 2.1 API.
<p>
The javax.servlet.jsp package contains a number of classes and
interfaces that describe and define the contracts between a JSP page
implementation class and the runtime environment provided for an
instance of such a class by a conforming JSP container.
</p>

<h2>JSP Page Implementation Object Contract</h2>
<p>
This section describes the basic contract between a JSP Page
implementation object and its container.
</p>
<p>
The main contract is defined by the classes 
{@link javax.servlet.jsp.JspPage}
and {@link javax.servlet.jsp.HttpJspPage}.
The {@link javax.servlet.jsp.JspFactory} class describes the mechanism to
portably instantiate all needed runtime objects,
and {@link javax.servlet.jsp.JspEngineInfo} provides basic information on
the current JSP container. Class {@link javax.servlet.jsp.JspApplicationContext}
stores application-scoped information relevant to JSP containers.
It was added in JSP 2.1 to support the integration of the unified
Expression Language.
</p>
<p>
None of these classes are intended to be used
by JSP page authors; an example of how these classes may be
used is included below.
</p>

<h2>Implicit Objects</h2>

The {@link javax.servlet.jsp.PageContext} object and the 
{@link javax.servlet.jsp.JspWriter}
are available by default as implicit objects.

<h2>Exceptions</h2>

<p>
The {@link javax.servlet.jsp.JspException} class is the base class for all JSP
exceptions.  The {@link javax.servlet.jsp.JspTagException} and 
{@link javax.servlet.jsp.SkipPageException} exceptions are used by the
tag extension mechanism.</p>
For JSP error pages, the {@link javax.servlet.jsp.ErrorData} class encapsulates information 
about the error.

</p>

<h2>An Implementation Example</h2>

<p> An instance of an implementation dependent subclass of the
{@link javax.servlet.jsp.PageContext} 
abstract base class can be created by a JSP implementation class at
the beginning of it's <code>_jspService()</code> method via an
implementation default {@link javax.servlet.jsp.JspFactory}.

<p>Here is one example of how to use these classes

<p>
<code>
<pre>
 public class foo implements Servlet {

 // ...

public void _jspService(HttpServletRequest request,
			HttpServletResponse response)
       throws IOException, ServletException {

    JspFactory  factory     = JspFactory.getDefaultFactory();
    PageContext pageContext = factory.getPageContext(
					this,
					request,
					response,
					null,  // errorPageURL
					false, // needsSession
					JspWriter.DEFAULT_BUFFER,
					true   // autoFlush
			        );

    // initialize implicit variables for scripting env ...

    HttpSession session = pageContext.getSession();
    JspWriter   out     = pageContext.getOut();
    Object      page    = this;

    try {
        // body of translated JSP here ...
    } catch (Exception e) {
        out.clear();
        pageContext.handlePageException(e);
    } finally {
        out.close();
	  factory.releasePageContext(pageContext);
    }
}
</pre>
</code>

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